Resonant converter and control

Abstract

An embodiment of non-isolated resonant converter includes resonant circuitry having inductive and capacitive elements configured to create electrical resonance when an input voltage is applied, a first electrical switch coupled to the resonant circuitry such that the first electrical switch conducts a current of the resonant circuitry, and voltage-monitoring circuitry coupled to the resonant circuitry and configured to determine when there is substantially no voltage across the first electrical switch. The non-isolated resonant converter further includes control circuitry configured to receive an input from the voltage-monitoring circuitry, and operate the first electrical switch. The control circuitry is configured to turn the first electrical switch on when substantially no voltage is detected across the first electrical switch.

What is claimed is: 
     
         1 . A non-isolated resonant converter comprising:
 resonant circuitry having inductive and capacitive elements configured to create electrical resonance when an input voltage is applied;   a first electrical switch coupled to the resonant circuitry such that the first electrical switch conducts a current of the resonant circuitry;   voltage-monitoring circuitry coupled to the resonant circuitry and configured to determine when there is substantially no voltage across the first electrical switch; and   control circuitry configured to:
 receive an input from the voltage-monitoring circuitry, and 
 operate the first electrical switch; 
   wherein the control circuitry is configured to turn the first electrical switch on when substantially no voltage is detected across the first electrical switch.   
     
     
         2 . The non-isolated resonant converter of  claim 1  wherein the first electrical switch comprises a GaN transistor. 
     
     
         3 . The non-isolated resonant converter of  claim 1  wherein the control circuitry is further configured to operate the first electrical switch in a mode in which the first electrical switch undergoes a plurality of on/off cycles over a period of time before being turned off. 
     
     
         4 . The non-isolated resonant converter of  claim 3  wherein the control circuitry is further configured to operate the first electrical switch such that, for each on/off cycle of the plurality of on/off cycles, a time the first electrical switch is turned on is progressively longer with each successive on/off cycle. 
     
     
         5 . The non-isolated resonant converter of  claim 3  wherein the control circuitry is further configured to periodically operate the mode to maintain a certain output power. 
     
     
         6 . The non-isolated resonant converter of  claim 1  wherein the control circuitry comprises modulation circuitry. 
     
     
         7 . The non-isolated resonant converter of  claim 6  wherein the modulation circuitry is programmable. 
     
     
         8 . The non-isolated resonant converter of  claim 1  wherein the control circuitry is further configured to receive a voltage feedback from an output of the non-isolated resonant converter. 
     
     
         9 . The non-isolated resonant converter of  claim 1  wherein the control circuitry is further configured to receive a current feedback from an output of the non-isolated resonant converter. 
     
     
         10 . The non-isolated resonant converter of  claim 1  further comprising a synchronous rectifier between the resonant circuitry and an output of the non-isolated resonant converter, wherein the synchronous rectifier comprises:
 a diode; 
 a second electrical switch in parallel with the diode; and 
 switching circuitry configured to operate the second electrical switch such that the second electrical switch is turned on when substantially no voltage across the diode is detected and current flow in the diode is positive in a direction from anode to cathode. 
 
     
     
         11 . The non-isolated resonant converter of  claim 10  wherein the switching circuitry is further configured to operate the second electrical switch such that the second electrical switch is turned off when the current flow is substantially zero. 
     
     
         12 . A method of providing electrical power conversion, the method comprising:
 providing a resonant converter with resonant circuitry having inductive and capacitive elements to create electrical resonance when an input voltage is applied to the resonant circuitry;   using voltage-monitoring circuitry to determine when there is substantially no voltage across an electrical switch coupled to the resonant circuitry; and   operating the electrical switch such that the electrical switch is turned on when substantially no voltage is detected across the electrical switch.   
     
     
         13 . The method of  claim 12  further comprising operating the electrical switch in a mode in which the electrical switch undergoes a plurality of on/off cycles over a period of time before being turned off. 
     
     
         14 . The method of  claim 13  further comprising operating the electrical switch such that, for each on/off cycle of the plurality of on/off cycles, a time the electrical switch is turned on is progressively longer with each successive on/off cycle. 
     
     
         15 . The method of  claim 12  further comprising operating a synchronous rectifier coupled to the resonant circuitry and an output of the resonant converter, the synchronous rectifier having a second electrical switch coupled in parallel to a diode, wherein operating the synchronous rectifier comprises operating the second electrical switch such that the second electrical switch is turned on when there substantially no voltage across the diode is detected and current flow in the diode is positive in a direction from anode to cathode. 
     
     
         16 . The method of  claim 15  further comprising operating the second electrical switch such that the second electrical switch is turned off when the current flow is detected to be zero. 
     
     
         17 . A resonant converter comprising:
 an input stage configured to receive an input voltage and comprising a first electrical switch coupled in series with a primary winding of a transformer;   an output stage configured to provide an output voltage and comprising a capacitive element coupled to secondary winding of the transformer such that electrical resonance can occur when the input voltage is applied;   voltage-monitoring circuitry coupled to the first electrical switch and configured to determine when there is substantially no voltage across the first electrical switch; and   control circuitry configured to:
 receive an input from the voltage-monitoring circuitry, and 
 operate the first electrical switch; 
   wherein the control circuitry is configured to turn the first electrical switch on when substantially no voltage is detected across the first electrical switch.   
     
     
         18 . The resonant converter of  claim 17  wherein either or both the input stage or the output stage includes an inductive element configured to provide the electrical resonance together with the capacitive element. 
     
     
         19 . The resonant converter of  claim 17  wherein the control circuitry is further configured to operate the first electrical switch in a mode in which the electrical switch undergoes a plurality of on/off cycles over a period of time before being turned off. 
     
     
         20 . The resonant converter of  claim 19  wherein the control circuitry is further configured to operate the first electrical switch such that, for each on/off cycle of the plurality of on/off cycles, a time the first electrical switch is turned on is progressively longer with each successive on/off cycle. 
     
     
         21 . The resonant converter of  claim 17  wherein the output stage further comprises a synchronous rectifier coupled to a node of an output of the resonant converter, wherein the synchronous rectifier comprises:
 a diode; 
 a second electrical switch in parallel with the diode; and 
 switching circuitry configured to operate the second electrical switch such that the second electrical switch is turned on when there is substantially no voltage across the diode and current flow in the diode is positive in a direction from anode to cathode. 
 
     
     
         22 . The resonant converter of  claim 17  wherein:
 the output stage further comprises a first synchronous rectifier and a second synchronous rectifier, wherein each of the first synchronous rectifier and the second synchronous rectifier comprise:
 a diode; and 
 an electrical switch in parallel with the diode; and 
 
 the resonant converter further includes switching circuitry configured to operate the electrical switch of each of the first synchronous rectifier and the second synchronous rectifier such that, for each of the first synchronous rectifier and the second synchronous rectifier the electrical switch is turned on when current flow in the diode is positive in a direction from anode to cathode. 
 
     
     
         23 . The resonant converter of  claim 17  further comprising clamping circuitry to control a voltage across the first electrical switch. 
     
     
         24 . The resonant converter of  claim 23  wherein the clamping circuitry comprises active clamping circuitry in which a clamping switch is turned on when a voltage across the first electrical switch reaches a threshold voltage. 
     
     
         25 . The resonant converter of  claim 23  wherein the clamping circuitry comprises:
 a clamp capacitor; and 
 an electrical clamp switch coupled in series with the clamp capacitor; 
 a sensor configured to measure a voltage across the first electrical switch; 
 a comparator circuit coupled with an output of the sensor and configured to compare the voltage across the first electrical switch with a reference voltage; and 
 a driver coupled to an output of the comparator circuit and configured to turn on the electrical clamp switch. 
 
     
     
         26 . The resonant converter of  claim 17  further wherein the control circuitry comprises modulation circuitry. 
     
     
         27 . The resonant converter of  claim 26  wherein the modulation circuitry is programmable.